draft-ietf-pim-v2-dm-00.txt   draft-ietf-pim-v2-dm-01.txt 
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forward state, allowing data to go down the branch previously in prune forward state, allowing data to go down the branch previously in prune
state. state.
The prune state contains source and group address information. When a The prune state contains source and group address information. When a
new member appears in a pruned area, a router can ``graft'' toward the new member appears in a pruned area, a router can ``graft'' toward the
source for the group, turning the pruned branch into forward state. source for the group, turning the pruned branch into forward state.
The forwarding branches form a tree rooted at the source leading to The forwarding branches form a tree rooted at the source leading to
all members of the group. This tree is called a source rooted tree. all members of the group. This tree is called a source rooted tree.
The flooding of datagrams followed by pruning of unwanted branches is The broadcast of datagrams followed by pruning of unwanted branches is
often referred to as a flood-and-prune cycle, typical of dense mode often referred to as a broadcast-and-prune cycle, typical of dense
protocols. The flood-and-prune mechanism in dense mode PIM uses a mode protocols. The broadcast-and-prune mechanism in dense mode PIM
technique called reverse path forwarding (RPF), in which a multicast uses a technique called reverse path forwarding (RPF), in which a
datagram is forwarded if the receiving interface is the one used to multicast datagram is forwarded if the receiving interface is the one
forward unicast datagrams to the source of the datagram. used to forward unicast datagrams to the source of the datagram.
Compared with multicast routing protocols with built-in topology Compared with multicast routing protocols with built-in topology
discovery mechanisms (e.g. DVMRP with its own RIP-like ``unicast'' discovery mechanisms (e.g. DVMRP with its own RIP-like ``unicast''
routing protocol), dense mode PIM has simplified design, and is not routing protocol), dense mode PIM has simplified design, and is not
hard-wired into a specific type of topology discovery protocol. hard-wired into a specific type of topology discovery protocol.
However, such simplification does incur more overhead and cause However, such simplification does incur more overhead and cause
flood-and-prune to occur on some links that could be avoided if broadcast-and-prune to occur on some links that could be avoided if
sufficient topology information is available, e.g. to decide whether sufficient topology information is available, e.g. to decide whether
each interface leads to any downstream neighbors for a particular each interface leads to any downstream neighbors for a particular
source. We chose to accept the additional overhead in favor of the source. We chose to accept the additional overhead in favor of the
simplification and flexibility gained by not depending on a specific simplification and flexibility gained by not depending on a specific
type of topology discovery protocol. type of topology discovery protocol.
In relation to sparse-mode PIM, dense-mode PIM differs in two In relation to sparse-mode PIM, dense-mode PIM differs in two
essential ways: 1) there are no periodic joins transmitted, only essential ways: 1) there are no periodic joins transmitted, only
explicit triggered grafts/prunes, and 2) there is no Rendezvous Point explicit triggered grafts/prunes, and 2) there is no Rendezvous Point
(RP). (RP).
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5 Protocol Description 5 Protocol Description
Dense mode PIM initiates forwarding state in routers when a source Dense mode PIM initiates forwarding state in routers when a source
begins to send. When a source sends multicast datagrams to a group G, begins to send. A source does not give any prior notifications to the
it does not give any prior notifications to the network. A receiving network when it sends multicast datagrams to a group G. If a receiving
router creates a forwarding entry for the source and group G, if it router does not already have a forwarding entry, it creates it for the
does not already have it. This is called a (S,G) entry. It includes source and group G. This forwarding entry is called a (S,G) entry. It
the following contents: source address, group address, the incoming includes the following contents: source address, group address, the
interface, a list of outgoing interfaces, a few flags and a few incoming interface, a list of outgoing interfaces, a few flags and a
timers. The incoming interface for (S,G) is determined by an RPF few timers. The incoming interface for (S,G) is determined by an RPF
lookup in the unicast routing table. The (S,G) outgoing interface list lookup in the unicast routing table. The (S,G) outgoing interface list
contains interfaces that have PIM routers present or host members for contains interfaces that have PIM routers present or host members for
group G. group G.
If a router creates a (S,G) entry with an empty outgoing interface If a router creates a (S,G) entry with an empty outgoing interface
list after receiving a multicast datagram, it must trigger a PIM-Prune list after receiving a multicast datagram, it must trigger a PIM-Prune
message toward the source S. This type of entry is called a negative message toward the source S. This type of entry is called a negative
cache entry. Negative cache entries can be found on leaf routers with cache entry. Negative cache entries can be found on leaf routers with
no local group members, or on routers where prune messages were no local group members, or on routers where prune messages were
received from downstream routers that caused the outgoing interface received from downstream routers that caused the outgoing interface
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[*] E.g. In DVMRP a leaf network for a source is de- [*] E.g. In DVMRP a leaf network for a source is de-
fined as one without downstream neighbor DVMRP routers. fined as one without downstream neighbor DVMRP routers.
Each DVMRP router is able to decide whether it has a Each DVMRP router is able to decide whether it has a
downstream DVMRP neighbor with respect to each source. downstream DVMRP neighbor with respect to each source.
This is due to the RIP-like mechanism used in its to- This is due to the RIP-like mechanism used in its to-
Deering,Estrin,Farinacci,Jacobson,Helmy,Meyer,Wei [Page 4] Deering,Estrin,Farinacci,Jacobson,Helmy,Meyer,Wei [Page 4]
A router determines it is a leaf by not receiving PIM Hello messages. A router determines it is a leaf by not receiving PIM Hello messages.
A leaf router can detect that there are no members downstream when it A leaf router can detect that there are no members downstream when it
is the only router on a network and there are no IGMP Host-Report is the only router on a network and there are no IGMP Host-Report
messages received from hosts. A leaf router should not populate a messages received from hosts. A router should not populate a
forwarding entry's outgoing interface list with such leaf network forwarding entry's outgoing interface list with a leaf network
without downstream members. interface without downstream members.
It should be noted that a non-leaf router in PIM dense-mode is not It should be noted that a non-leaf router in PIM dense-mode is not
necessarily a non-leaf node on a particular multicast forwarding tree. necessarily a non-leaf node on a particular multicast forwarding tree.
There are topologies where two parallel routers are connected to a There are topologies where two parallel routers are connected to a
common LAN where none of the routers uses the other one to reach a common LAN where none of the routers uses the other one to reach a
source. Therefore both routers will be leaves of any forwarding trees source. Therefore both routers will be leaves of any forwarding trees
rooted at the source. When there are no group members on this LAN, rooted at the source. When there are no group members on this LAN,
both routers must not forward packets onto it. This is achieved by both routers must not forward packets onto it. This is achieved by an
prune messages sent on the LAN as a result of an assert process. assert process. Please see section 5.5 for more details.
Please
A dense mode PIM implementation must take proper actions when a non- A dense mode PIM implementation must take proper actions when a non-
leaf router becomes a leaf router. When the last PIM neighbor on an leaf router becomes a leaf router. When the last PIM neighbor on an
interface goes away and turns the connected subnet into a leaf interface goes away and turns the connected subnet into a leaf
network, the router should delete that interface from the outgoing network, the router should delete that interface from the outgoing
interface lists of all groups without attached group members. interface lists of all groups without attached group members.
5.2 Pruning of branches 5.2 Pruning of branches
5.2.1 Pruning on multi-access LANs and prune-override 5.2.1 Pruning on multi-access LANs and prune-override
To avoid PIM-Prune message storms, PIM-Prune messages are never sent To avoid PIM-Prune message storms, PIM-Prune messages must not be sent
on LANs in response to a received multicast packet that is associated on LANs in response to each received multicast packet that is
with an existing negative cache entry. associated with an existing negative cache entry.
A prune is sent upstream when a router creates a (S,G) entry with an A prune is sent upstream when a router creates a (S,G) entry with an
empty outgoing interface list, or when the outgoing interface list empty outgoing interface list, or when the outgoing interface list
becomes empty. [*] becomes empty. [*]
Prune information is flushed periodically. This causes multicast Prune information is flushed periodically. This causes multicast
datagrams to be sent in RPF mode again which in turn triggers prune datagrams to be sent in RPF mode again which in turn triggers prune
messages. messages.
When a prune message is sent onto an upstream LAN, it is data link When a prune message is sent onto an upstream LAN, it is data link
multicast and IP addressed to the all PIM routers group address multicast and IP addressed to the all PIM routers group address
224.0.0.13. The router to process the prune will be indicated by 224.0.0.13. The router to process the prune will be indicated by
inclusion of its address in the "Address" field of the message. This inclusion of its address in the "Address" field of the message. This
address is obtained by an RPF look up for the source. When the prune
_________________________ _________________________
pology discovery (or ``unicast routing'') protocol. pology discovery (or ``unicast routing'') protocol.
[*] I.e. the set of forwarding interfaces in the out- [*] I.e. the set of forwarding interfaces in the out-
going interface list is NULL. going interface list is NULL.
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address is obtained by an RPF look up for the source. When the prune
message is sent, the expected upstream router will schedule a deletion message is sent, the expected upstream router will schedule a deletion
request of the LAN from its outgoing interfaces for the (S,G) entry request of the LAN from its outgoing interfaces for the (S,G) entry
from the prune list. The suggested delay time before deletion should from the prune list. The suggested delay time before deletion should
be greater than 3 seconds. The default prune delay time is 3 seconds. be greater than 3 seconds. The default prune delay time is 3 seconds.
Other routers on the LAN will hear the prune message and respond with Other routers on the LAN will hear the prune message and respond with
a join if they still expect multicast datagrams from the expected a join if they still expect multicast datagrams from the expected
upstream router. The PIM-Join message is data link multicast and IP upstream router. The PIM-Join message is data link multicast and IP
addressed to the all PIM routers group address 224.0.0.13. The router addressed to the all PIM routers group address 224.0.0.13. The router
to process the join will be indicated by inclusion of its address in to process the join will be indicated by inclusion of its address in
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entry. entry.
However, if the prune-override join message is lost, the deletion will However, if the prune-override join message is lost, the deletion will
occur and there will be no data delivery for the amount of time the occur and there will be no data delivery for the amount of time the
interface remains in prune state. To reduce the probability of this interface remains in prune state. To reduce the probability of this
occurance, a router that has scheduled to prune the interface off is occurance, a router that has scheduled to prune the interface off is
required to immediately send a prune onto the interface. This gives required to immediately send a prune onto the interface. This gives
other routers another chance to hear the prune, and to respond with a other routers another chance to hear the prune, and to respond with a
join. join.
Finally, equal-cost paths leading to a LAN presents a special case for Additionally, equal-cost paths leading to a LAN presents a special
join/prune processing. When an upstream router is chosen by an RPF case for join/prune processing. When an upstream router is chosen by
lookup there may be equal-cost paths to reach the source. The higher an RPF lookup there may be equal-cost paths to reach the source. The
IP addressed system is always chosen. If the unicast routing protocol higher IP addressed system is always chosen. If the unicast routing
does not store all available equal-cost paths in the routing table, protocol does not store all available equal-cost paths in the routing
the "Address" field may contain the address of the wrong upstream table, the "Address" field may contain the address of the wrong
router. To avoid this situation, the "Address" field may optionally be upstream router. To avoid this situation, the "Address" field may
set to 0.0.0.0 which means that all upstream routers (the ones that optionally be set to 0.0.0.0 which means that all upstream routers
have the LAN as an outgoing interface for the (S,G) entry) may process (the ones that have the LAN as an outgoing interface for the (S,G)
the packet. entry) may process the packet.
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5.2.2 Pruning a Point-to-point link 5.2.2 Pruning a Point-to-point link
PIM-Prune messages received on a point to point link are not delayed PIM-Prune messages received on a point to point link are not delayed
before processing as they are in the LAN procedure. If the prune is before processing as they are in the LAN procedure. If the prune is
received on an interface that is in the outgoing interface list, it is received on an interface that is in the outgoing interface list, it is
deleted immediately. deleted immediately.
Prunes may be rate-limited on point-to-point interfaces when a Prunes may be rate-limited on point-to-point interfaces when a
multicast datagram is received for a negative cache entry. multicast datagram is received for a negative cache entry, or if the
point-to-point interface receiving the datagram is not the RPF
interface toward the source.
5.3 New members joining an existing group 5.3 New members joining an existing group
If a router is directly connected to a host that wants to become a If a router is directly connected to a host that wants to become a
member of a group, the router may send a PIM-Graft message toward member of a group, the router may send a PIM-Graft message toward
known sources. This allows join latency to be reduced below that known sources. This allows join latency to be reduced below that
indicated by the relatively large timeout value suggested for prune indicated by the relatively large timeout value suggested for prune
information. information.
The host indicates its interest in group G by sending an IGMP report. The host indicates its interest in group G by sending an IGMP report.
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PIM-Graft message is the only PIM message that uses a positive PIM-Graft message is the only PIM message that uses a positive
acknowledgment strategy. Senders of PIM-Graft messages unicast them to acknowledgment strategy. Senders of PIM-Graft messages unicast them to
their upstream RPF neighbors. The neighbor processes each (S,G) and their upstream RPF neighbors. The neighbor processes each (S,G) and
immediately acknowledges each (S,G) in a PIM-GraftAck message. This is immediately acknowledges each (S,G) in a PIM-GraftAck message. This is
relatively easy, since the receiver simply changes the PIM message relatively easy, since the receiver simply changes the PIM message
type from Graft to Graft-Ack and unicasts the original packet back to type from Graft to Graft-Ack and unicasts the original packet back to
the source. The sender periodically retransmits the PIM-Graft message the source. The sender periodically retransmits the PIM-Graft message
for any (S,G) that has not been acknowledged. The interval between for any (S,G) that has not been acknowledged. The interval between
each retransmission is 3 seconds. Note that the sender need not keep a each retransmission is 3 seconds. Note that the sender need not keep a
retransmission list for each neighbor since PIM-Grafts are only sent retransmission list for each neighbor since PIM-Grafts are only sent
to the RPF neighbor. Only the (S,G) entry needs to be tagged for
retransmission.
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to the RPF neighbor. Only the (S,G) entry needs to be tagged for
retransmission.
5.4 Designated Router Election 5.4 Designated Router Election
Dense mode PIM itself does not need the function of a designated Dense mode PIM itself does not need the function of a designated
router (DR). But a DR is needed on multi-access LANs running IGMP router (DR). But a DR is needed on multi-access LANs running IGMP
version 1, which relies on a routing protocol to select a query router version 1, which relies on a routing protocol to select a query router
for the purpose of sending IGMP Host-Query messages. Dense-mode PIM for the purpose of sending IGMP Host-Query messages. Dense-mode PIM
designated router (DR) election has the same procedure sparse-mode PIM designated router (DR) election has the same procedure sparse-mode PIM
uses. uses.
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using different unicast protocols where this might not be the case). using different unicast protocols where this might not be the case).
The upstream router elected is the one that has the best metric to the The upstream router elected is the one that has the best metric to the
source. When a packet is received on an outgoing interface, a router source. When a packet is received on an outgoing interface, a router
will send an Assert packet on the LAN indicating what metric it uses will send an Assert packet on the LAN indicating what metric it uses
to reach the source of the data packet. If metrics are comparable, the to reach the source of the data packet. If metrics are comparable, the
router with the best metric will become the forwarder. Incomparable router with the best metric will become the forwarder. Incomparable
metrics will be discussed later in this section when metric preference metrics will be discussed later in this section when metric preference
is described. All other upstream routers will delete the interface is described. All other upstream routers will delete the interface
from their outgoing interface list. The downstream routers also do the from their outgoing interface list. The downstream routers also do the
Deering,Estrin,Farinacci,Jacobson,Helmy,Meyer,Wei [Page 8]
comparison in case the forwarder is different than the RPF neighbor. comparison in case the forwarder is different than the RPF neighbor.
This is important so downstream routers send subsequent Prunes or This is important so downstream routers send subsequent Prunes or
Grafts to the correct neighbor. Grafts to the correct neighbor.
Deering,Estrin,Farinacci,Jacobson,Helmy,Meyer,Wei [Page 8]
Associated with the metric is a metric preference value. This is Associated with the metric is a metric preference value. This is
provided to deal with the case where the upstream routers may run provided to deal with the case where the upstream routers may run
different unicast routing protocols. The numerically smaller metric different unicast routing protocols. The numerically smaller metric
preference is always preferred. The metric preference should be preference is always preferred. The metric preference should be
treated as the high-order part of an Assert metric comparison. treated as the high-order part of an Assert metric comparison.
Therefore, a metric value can be compared with another metric value Therefore, a metric value can be compared with another metric value
provided both metric preferences are the same. A metric preference can provided both metric preferences are the same. A metric preference can
be assigned per unicast routing protocol and needs to be consistent be assigned per unicast routing protocol and needs to be consistent
for all PIM routers on the LAN. for all PIM routers on the LAN.
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1 Compare metric received in Assert with the one you would have 1 Compare metric received in Assert with the one you would have
advertised in an Assert. If the value in the Assert is less than advertised in an Assert. If the value in the Assert is less than
your value, prune the interface. If the value is the same, and your value, prune the interface. If the value is the same, and
your address is less than the Assert sender, prune the interface. your address is less than the Assert sender, prune the interface.
2 If you have won the election and there are directly connected 2 If you have won the election and there are directly connected
members on the LAN, keep the interface in your outgoing interface members on the LAN, keep the interface in your outgoing interface
list. You are the forwarder for the LAN. list. You are the forwarder for the LAN.
Deering,Estrin,Farinacci,Jacobson,Helmy,Meyer,Wei [Page 9]
3 If you have won the election but there are no directly connected 3 If you have won the election but there are no directly connected
members on the LAN, schedule to prune the interface. The LAN might members on the LAN, schedule to prune the interface. The LAN might
be a stub LAN with no members (and no downstream routers). If no be a stub LAN with no members (and no downstream routers). If no
subsequent Joins are received, delete the interface from the subsequent Joins are received, delete the interface from the
Deering,Estrin,Farinacci,Jacobson,Helmy,Meyer,Wei [Page 9]
outgoing interface list. Otherwise keep the interface in your outgoing interface list. Otherwise keep the interface in your
outgoing interface. You are the forwarder for the LAN. outgoing interface. You are the forwarder for the LAN.
4 The assert winner sends an assert with its own metric on the LAN, 4 The assert winner sends an assert with its own metric on the LAN,
so that all other routers know who the winner is. so that all other routers know who the winner is.
Asserts received on incoming interface: Asserts received on incoming interface:
1 Downstream routers will select the upstream router with the 1 Downstream routers will select the upstream router with the
smallest metric as their RPF neighbor. If two metrics are the smallest metric as their RPF neighbor. If two metrics are the
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multicast routing entry itself, one for each pruned interface in the multicast routing entry itself, one for each pruned interface in the
outgoing interface list and one to time out information about upstream outgoing interface list and one to time out information about upstream
assert winner (Assert_timer). An outgoing interface in forward state assert winner (Assert_timer). An outgoing interface in forward state
does not time out or change state without external events. The does not time out or change state without external events. The
outgoing interface stays in forward state in the list as long as there outgoing interface stays in forward state in the list as long as there
is a group member connected, or there is a downstream PIM neighbor is a group member connected, or there is a downstream PIM neighbor
that has not sent a prune to it. The interface is deleted from the that has not sent a prune to it. The interface is deleted from the
outgoing interface list if it is on a leaf network and there is no outgoing interface list if it is on a leaf network and there is no
connected member. The interface timer for a pruned interface should be connected member. The interface timer for a pruned interface should be
started with the holdtime in the prune message (also referred to as started with the holdtime in the prune message (also referred to as
Deering,Estrin,Farinacci,Jacobson,Helmy,Meyer,Wei [Page 10]
the prune timer). the prune timer).
When a (S,G) entry is in forwarding state, its expiration timer is set When a (S,G) entry is in forwarding state, its expiration timer is set
to [Data-Timeout], as specified in the companion sparse mode to [Data-Timeout], as specified in the companion sparse mode
Deering,Estrin,Farinacci,Jacobson,Helmy,Meyer,Wei [Page 10]
specification [PIMSM], which is 210 seconds by default. This timer is specification [PIMSM], which is 210 seconds by default. This timer is
restarted when a data packet is being forwarded. The (S,G) entry is restarted when a data packet is being forwarded. The (S,G) entry is
deleted if this timer expires. deleted if this timer expires.
Once all interfaces in the outgoing interface list are pruned, the Once all interfaces in the outgoing interface list are pruned, the
(S,G)'s expiration timer should be set to the maximum prune timer (S,G)'s expiration timer should be set to the maximum prune timer
among all its outgoing interfaces. During this time the entry is known among all its outgoing interfaces. During this time the entry is known
as a negative cache entry. as a negative cache entry.
If the prune timers on different outgoing interfaces are different, If the prune timers on different outgoing interfaces are different,
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this happens, a graft should be triggered upstream. When a negative this happens, a graft should be triggered upstream. When a negative
cache entry turns into a forward entry, the entry timer should be cache entry turns into a forward entry, the entry timer should be
restarted with the default expiration timer. Once the (S,G) entry restarted with the default expiration timer. Once the (S,G) entry
times out, it will be recreated when the next multicast packet or join times out, it will be recreated when the next multicast packet or join
arrives. arrives.
The prune message sent upstream contains a holdtime. Its default value The prune message sent upstream contains a holdtime. Its default value
is [Data-Timeout], except when the Assert timer is also running, the is [Data-Timeout], except when the Assert timer is also running, the
holdtime in the prune message is set to the smaller value between the holdtime in the prune message is set to the smaller value between the
prune holdtime the system uses, and the remaining assert timer value prune holdtime the system uses, and the remaining assert timer value
before its expiration. The Assert Timer has a default value of 210 before its expiration. The Assert Timer is started with a default
seconds. value of 210 seconds.
5.7 Adapting to unicast route changes 5.7 Adapting to unicast route changes
When unicast route changes occur, the RPF interface for many (S,G) When unicast route changes occur, the RPF interface for many (S,G)
entries will also change. The following should be done for the entries will also change. The following should be done for the
affected entries: affected entries:
1 A prune should be sent toward the old incoming interface; 1 A prune should be sent toward the old incoming interface;
2 A graft should be sent to the new RPF neighbor. 2 A graft should be sent to the new RPF neighbor.
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received on an outgoing interface corresponding to the (S,G) or (*,G) received on an outgoing interface corresponding to the (S,G) or (*,G)
associated with the source. This message is used in both dense-mode associated with the source. This message is used in both dense-mode
and sparse-mode PIM. For packet format, refer to PIM sparse-mode and sparse-mode PIM. For packet format, refer to PIM sparse-mode
specification. specification.
6.7 PIM-Graft Message 6.7 PIM-Graft Message
This message is sent by a downstream router to a neighboring upstream This message is sent by a downstream router to a neighboring upstream
router to reinstate a previously pruned branch of a source tree. This router to reinstate a previously pruned branch of a source tree. This
is done for dense-mode groups only. The format is the same as a is done for dense-mode groups only. The format is the same as a
Join/Prune message, except that the value in the type field is 6. Join/Prune message, except that the value in the type field is 6. The
source address hsould be included in teh join section of the message.
The holdtime field is unused, and is ignored when a graft is received.
Deering,Estrin,Farinacci,Jacobson,Helmy,Meyer,Wei [Page 13] Deering,Estrin,Farinacci,Jacobson,Helmy,Meyer,Wei [Page 13]
6.8 PIM-Graft-Ack Message 6.8 PIM-Graft-Ack Message
Sent in response to a received Graft message. The Graft-Ack is only Sent in response to a received Graft message. The Graft-Ack is only
sent if the interface in which the Graft was received is not the sent if the interface in which the Graft was received is not the
incoming interface for the respective (S,G). This is done for dense- incoming interface for the respective (S,G). This is done for dense-
mode groups only. The format is the same as Join/Prune message, except mode groups only. The format is the same as Join/Prune message, except
that the value of the message type field is 7. that the value of the message type field is 7. The ``Encoded-Unicast-
Upstream Neighbor Address'' field is unused and needs not be checked
when this message is received. The holdtime field in the packet is
ignored when received.
7 Acknowledgement 7 Acknowledgement
Thanks to Manoj Leelanivas, Sangeeta Mukherjee, Nitin Jain and many Thanks to Manoj Leelanivas, Sangeeta Mukherjee, Nitin Jain and many
members of the IDMR working group for their helpful comments. members of the PIM/IDMR working group for their helpful comments.
8 References 8 References
[Deering91] S.E. Deering. Multicast Routing in a Datagram [Deering91] S.E. Deering. Multicast Routing in a Datagram
Internetwork. PhD thesis, Electrical Engineering Dept., Stanford Internetwork. PhD thesis, Electrical Engineering Dept., Stanford
University, December 1991. University, December 1991.
[DVMRP] RFC 1075, Distance Vector Multicast Routing Protocol. [DVMRP] RFC 1075, Distance Vector Multicast Routing Protocol.
Waitzman, D., Partridge, C., Deering, S.E, November 1988 Waitzman, D., Partridge, C., Deering, S.E, November 1988
skipping to change at line 656 skipping to change at line 662
cisco Systems, Inc cisco Systems, Inc
170 West Tasman Drive 170 West Tasman Drive
San Jose, CA95134 San Jose, CA95134
meyer@cisco.com meyer@cisco.com
Liming Wei Liming Wei
cisco Systems Inc cisco Systems Inc
170 West Tasman Drive 170 West Tasman Drive
San Jose, CA 95134 San Jose, CA 95134
lwei@cisco.com lwei@cisco.com
Deering,Estrin,Farinacci,Jacobson,Helmy,Meyer,Wei [Page 15]
Deering,Estrin,Farinacci,Jacobson,Helmy,Meyer,Wei [Page 16]
 End of changes. 

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